The cost of diesel fuel is a major contributor to the operating cost of mining or manufacturing sites that operate diesel driven equipment. Ideally, diesel engines would operate at 100% efficiency with the fuel burning completely and instantaneously when the piston is at the top of the power stroke. At this point, the cylinder volume is at its minimum and a maximum amount of energy (as heat) would be extracted from the fuel and used to power the engine. However, in reality, no fuel combustion is 100% efficient and even modern diesel engines have a thermal efficiency of only 35-40%. In practice, the fuel energy is made available more gradually (by slower burn), cylinder pressure rises and falls well short of the ideal.
Much energy is lost as heat from the engine exhaust. The rest of the energy is lost by radiation or is lost to the cooling system as it removes excess heat from the engine.
It seems unlikely that further on-going engine design improvements can offer any major improvements to thermal efficiency. Although there has been an increase in engine performance, the performance characteristics of modern diesel fuel have remained relatively stable over recent years.
However, improvements in fuel technology still offer potential area savings and for the past 2 decades, attempts have been made to chemically improve fuels. For example, attempts have been made to chemically improve the overall combustion reaction by the addition of trace amounts of a ferrous picrate catalyst.
Over the past two decades of commercial use by the mining industry in Australia, for instance, ferrous picrate use has resulted in fuel savings of 6-8% for mine mobile equipment and 3-5% for large medium speed engines in power generation service.
An intensive study involving approximately fifty large diesel power generation sets was conducted by Fuel Technology Pty Ltd, a company specializing in combustion and fuel technology. The study showed that when using catalyst treated fuel, exhaust temperatures were reduced an average 9.2° C. under static load conditions. This result is interpreted to mean that use of the catalyst provides more useable heat from the fuel, so that less fuel is used and less heat is wasted via the exhaust.
In light of its efficacy, efforts have been made to develop more commercially attractive methods for producing ferrous picrate. For some purposes, such as addition to carbonaceous fuel, it is highly desirable that ferrous picrate be substantially free from ferric compounds and other undesirable impurities. However, it has proved difficult to produce ferrous picrate free from such impurities by a commercially acceptable method.
Furthermore, most of the processes for purification described in the patent literature involve several steps, resulting in relatively low yields and rendering the product expensive.
Another problem associated with the processes of the prior art is that they use toxic or hazardous reactants, such as ferrous picrate and picric acid which in the solid state may be explosive. Reactants of this type require special handling with due regard to appropriate safety precautions which further increases the cost of ferrous picrate manufacture.
Accordingly, efforts have been made to find commercially acceptable processes for manufacturing comparatively pure ferrous picrate. For example, U.S. Pat. No. 5,359,103 describes a process for preparing ferrous picrate comprising reacting picric acid in solution in a straight or branched chain aliphatic alcohol and an aromatic solvent with iron carbonyl at a temperature between 10 and 120° C. This process has a high yield of ferrous picrate and has relatively few steps. However, the major disadvantage is that it uses iron carbonyl which is highly toxic and requires special equipment and expertise to handle, factors that contribute significantly to the manufacturing cost and limit use of the process to specialized factories.
Another example of a process for preparation of ferrous picrate is described in Australian Patent No. 624964 (57904/90). This process includes the steps of (a) reacting an aqueous solution of a ferrous salt with an alkali hydroxide to produce a ferrous hydroxide precipitate, (b) removing water and by-products from the ferrous hydroxide, (c) adding the ferrous hydroxide and a straight or branched chain aliphatic alcohol to a solution of picric acid in an aromatic solvent from which water has been removed to produce a solution of ferrous picrate, and (d) removing any insoluble material from the solution, wherein the steps are performed under an inert atmosphere.
Another method for producing ferrous picrate comprises reacting, under non-oxidizing conditions, ferrous carbonate free from ferric compounds with a water-free solution of picric acid in a solvent medium selected from an aromatic hydrocarbon solvent, a mixture of aromatic hydrocarbon solvents, a straight-or a branched-chain aliphatic alcohol, a mixture of straight-and/or branched-chain aliphatic alcohols, and a mixture of straight-and/or branched-chain aliphatic alcohols with aromatic hydrocarbon solvents to produce a solution of ferrous picrate.
Producers of industrial chemicals, such as ferrous picrate, continually attempt to improve their processes and obtain commercial savings in terms of production costs and the input of time and energy to their processes. Some commercial savings can be derived from minimizing the use or handling of hazardous materials, reducing energy input to the process and producing products of good purity so that the need for further the purification is minimized or eliminated.
Thus, an ongoing need exists for improvements to ferrous picrate production processes in terms of commercial efficiency, product purity and product storage stability. In particular, a need exists for a process for producing ferrous picrate that is comparatively simple and commercially viable, yet produces comparatively few ferric compounds and other impurities by comparison with the ferrous picrate production methods of the prior art. A need also exists for the ferrous picrate product to exhibit storage stability when incorporated into carbonaceous fuels.